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Cisco ASA Series CLI Configuration Guide
APPENDIX
1
Addresses, Protocols, and Ports
This appendix provides a quick reference for IP addresses, protocols, and applications. This appendix
includes the following sections:
• IPv4 Addresses and Subnet Masks, page 1-1
• IPv6 Addresses, page 1-5
• Protocols and Applications, page 1-11
• TCP and UDP Ports, page 1-11
• Local Ports and Protocols, page 1-14
• ICMP Types, page 1-15
IPv4 Addresses and Subnet Masks
This section describes how to use IPv4 addresses in the ASA. An IPv4 address is a 32-bit number written
in dotted-decimal notation: four 8-bit fields (octets) converted from binary to decimal numbers,
separated by dots. The first part of an IP address identifies the network on which the host resides, while
the second part identifies the particular host on the given network. The network number field is called
the network prefix. All hosts on a given network share the same network prefix but must have a unique
host number. In classful IP, the class of the address determines the boundary between the network prefix
and the host number.
This section includes the following topics:
• Classes, page 1-1
• Private Networks, page 1-2
• Subnet Masks, page 1-2
Classes
IP host addresses are divided into three different address classes: Class A, Class B, and Class C. Each
class fixes the boundary between the network prefix and the host number at a different point within the
32-bit address. Class D addresses are reserved for multicast IP.
• Class A addresses (1.xxx.xxx.xxx through 126.xxx.xxx.xxx) use only the first octet as the network
prefix.
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